Je. Schmidt et Bk. Ahring, EFFECTS OF HYDROGEN AND FORMATE ON THE DEGRADATION OF PROPIONATE AND BUTYRATE IN THERMOPHILIC GRANULES FROM AN UPFLOW ANAEROBIC SLUDGE BLANKET REACTOR, Applied and environmental microbiology, 59(8), 1993, pp. 2546-2551
Degradation of propionate and butyrate in whole and disintegrated gran
ules from a thermophilic (55-degrees-C) upflow anaerobic sludge blanke
t reactor fed with acetate, propionate, and butyrate as substrates was
examined. The propionate and butyrate degradation rates in whole gran
ules were 1.16 and 4.0 mumol/min/g of volatile solids, respectively, a
nd the rates decreased 35 2nd 25%, respectively, after disintegration
of the granules. The effect of adding different hydrogen-oxidizing bac
teria (both sulfate reducers and methanogens), some of which used form
ate in addition to hydrogen, to disintegrated granules was tested. Add
ition or either Methanobacterium thermoautotrophicum DELTAH, a hydroge
n-utilizing methanogen that does not use formate, or Methanobacterium
sp. strain CB12, a hydrogen- and formate-utilizing methanogen, to disi
ntegrated granules increased the degradation rate of both propionate a
nd butyrate. Furthermore, addition of a thermophilic sulfate-reducing
bacterium (a Desulfotomaculum sp. isolated in our laboratory) to disin
tegrated granules improved the degradation or both substrates even mor
e than the addition of methanogens. By monitoring the hydrogen partial
pressure in the cultures, a correlation between the hydrogen partial
pressure and the degradation rate of propionate and butyrate was obser
ved, showing a decrease in the degradation rate with increased hydroge
n partial pressure. No significant differences in the stimulation of t
he degradation rates were observed when the disintegrated granules wer
e supplied with methanogens that utilized hydrogen only or hydrogen an
d formate. This indicated that interspecies formate transfer was not i
mportant for stimulation of propionate and butyrate degradation.